Hierarchical Photothermal Network Spontaneously Facilitates Co‐Extraction of Clean Water and Boron

Abstract Resources, energy, and food are interconnected global challenges. Herein, a double‐layer hierarchical photothermal network (HPN) is designed to co‐harvest clean water and boron. As is known, this is the first to achieve the above aims together. As a concept demonstration, the graphene oxide (GO) hydrogel with vertically aligned GO nanosheets served as the upper layer for light adsorption, while the Mg(OH) 2 /GO hydrogel acted as the bottom layer for boron extraction. HPN demonstrated a high evaporation rate of 1.87 kg m −2 h −1 , with an evaporation efficiency of 89.9% under 1 sun. Combined with the evaporation‐induced convection effect, localization concentration field, and temperature field, HPN showed a record boron extraction capacity of 789.5 mg m −2 under solar irradiation, versus just 112.16 mg m −2 under dark conditions. The contributions of these enhanced factors are 59.6%, 30.1%, and 10.3%, respectively. Ultimately, the extracted boron significantly increased the germination rate and growth of irrigated crops. In conclusion, HPN offers a novel approach to boron extraction and provides an innovative solution to advance the achievement of Sustainable Development Goals (SDGs).